Process of and apparatus for manufacturing liquid and solid carbon dioxide



F. B. HUNT Aug. 27, 1935;

PROCESS OF AND APPARATUS FOR MANUFACTURING LIQUID AND SOLID CARBON DIOXIDE Filed March 26, 1932 Q I QM a 2a m R Nu m R i Q wmm may Mn aw INVENTOR. Franklin 5. Hunt,

ATTORNE Y5 Patented Aug. 27, 19 35 UNITED STATES PROCESS OF APPARATUS FOR MANU- FACTURING LIQUID AND SOLID CARBON DIOXIDE Franklin B. Hunt, Chicago, 111., assignor to The Liquid Carbonic Corporation, Chicago, 111., a corporation of Delaware Application March' 26, 1932, Serial No. 601,313

14 Claims. (Cl. 62-179) The present application relates to aprocess of and apparatus for manufacturing liquid and solid carbon dioxide, and a primary object thereof is so to improve the efficiency of a known process,

primarily by energy conservation and utilization,

v objects of the invention will appear as the de-' as to substantially eliminate the necessity for purchasing any power. Further and subsidiary scription proceeds.

To the accomplishment of the abo and related objects, my invention may be em died in the forms illustrated in the accompanying draw ing, attention being called to the fact, however,

that the drawing is illustrative only, and that I change may be made in the specific. constructions illustrated'and described, or in the specific steps stated, so long as the scope of the appended claims is not violated.

Fig. 1 is a diagrammatic illustration of apparatus arranged in accordance with my invention and capable of producing liquid carbon dioxide, the drawing being more in thenature of a flow sheet than of an illustration of mechanism; and

Fig. 2 is a diagrammatic illustration of theelements which may be added -to the organization of Fig. 1 to -carry the liquid carbon dioxide on into the solid phase.

Referring more particularly to the drawing, it will be seen that I have illustrated a furnace or combustion chamber ID with which is associated a boiler H. A flue l2 conducts the gaseous products of combustion from said combustion chamber ID to a scrubber chamber. l3, entering said chamber at the bottom; and a conduit I4 connects the upper end of said chamber l3 with the bottom of a second scrubber l5, to lead the gases washed in the chamber 13 to said chamber l5, where a second scrubbing operation takes place.

A pipe line' I6 is connected to a suitable source of water (not shown) and said pipe line comprises a pair of branches I6 and I6", respectively, ente'ring the upper ends of the chambers I3 and I5. Water outlet branches l1 and I1", leading respectively from the chambers l3 and I5 join in a waste pipe H. A conduit l8 leads from the upper end of scrubber chamber I5 to conduct scrubbed gases from said chamber,-a blower l9 providing The gases which are not absorbed in thechamber 20 pass from the upper end thereof through a conduit 2| and into the lower end of a second absorber 22, likewise containing an absorbing medium; and a conduit 23 leads from 'the upper' end of said chamber 22 to conduct therefrom the waste gases which are not absorbed in said chambers 20 and 22.

The solution within the chambers 20 and 22 absorbs from the gaseous mixture a considerable proportion of the carbon dioxide therein.

In the art, the term strong lye is used to denote a sodium carbonate solution which has absorbed a relatively large quantity of carbon dioxide; and the term weak lye isused to refer to a solution having very little, if any, carbon dioxide absorbed therein. The terms will be so used herein.

A pipe 24 is connected to the lower end of the chamber to conduct therefrom the strong lye, a pump 25 being providedto force the strong lye through a pipe 26 and through one end 21 ofa heat interchanger 28, and thence through a pipe 29 into the lye boiler 30.

A second pipe 3| is connected to the lower end of chamber 20 and to a secondpump 32, said .pump effecting circulation of the lye solution through the pipe 3| and a pipe 33; said pipe 33 discharging into the upper end of the absorber 20, whereby a falling curtain of lye solution is provided in the absorber 20 through which the rising gases must pass.

Similarly, a pipe 34 is connected to the lower end of the absorber 2'2, and a pump 35 enforces circulation through the pipe 34 and a pipe 36 discharging into the upper end of the absorber 22. A pipe 31 provides for flow of relatively strong lye from the absorber 22 into the absorber 20.

Combustion of fuel in the chamber Ill produces the carbon dioxide which is separated from the other flue gases in the manner just described, and

it also produces heat which is used to evaporate water in the boiler II. A pipe 38 conducts the steam so formed to a steam engine 39, and it is customary in the art to exhaust the steam from the engine 39 at about'250" F. The steam so exhausted is led through a pipe 40 to heater coils 4| associated with the boiler 30, and there substantially allof such exhaust steam is condensed in the process of heating the solution in said boiler. The condensate is returned through a pipe 42 to the main boiler l I.

As the solution in the boiler "is heated, carbon dioxide and steam are driven ofl at a temperature of about 225 to 230 F., and under ordinary con- 40 A a 1 wherein ammonia is absorbed in water, A-pump ditions, the mass of water so evaporated ranges from one to three times the mass of carbon di- 1 oxide driven off. It is customary to separate the carbon dioxide from. this steam by" condensing the steam, using running water to cool the mixture and thereby wasting the heat energy stored in the steam and carbon dioxide.

After the carbondioxide concentration of the solution has been suitably reduced by boiling, the' weak lye is returned, through a pipe line 43, said weak lye solution passing through the opposite end 44 of the heat exchanger-2B, and being returned by thepipe 45 to the lower end of the absorber 22. The steam and carbon dioxide driven off from the solution in the boiler passes out through. a pipe 46.-

a refrigerating effect." As is illustrated in the.

drawing, the pipe 46 leads to the heating unit 41 of the' generator 48 of such a refrigerating system. In said generator, the mixture is cooled,

and the steam therein is condensed. The condensate and carbonv dioxide are conducted from said coil 41 through a pipe 49 to a separator 50 where the condensate is separated from the calfbon dioxide, and, the carbon dioxide is led thence through a pipe ii to a compressor 52 driven byjthe engine 39. Thecbndensate is led from the sep- 1 arator 50 througha pipe 4 absorber 22.

53 to the lower end of the Ammonia absorption refrigerating systems are known. Such a system comprises an absorber draws the aqueous ammonia solution from the' absorber 60 through apipe GI, and force'sit through a pipe 63., to,and through a rectifier,

and thence through a pipe to and through aheat exchanger 66 I hence the solution passes through a pipe 61 to the other end- 54 of the generator 48. There, the ammonia solution is heated by the mixture driven oif in the boiler an, whereby ammonia vapor and a small amount of water vapor is driven oitirom the ammonia solution.

' This mixture cit-gaseous ammonia and water vapor passes from the generator through the pipe I2 and thence through the rectifier 64, In such rectifier, the solution passing through the'pipes.

"63 and 55- as above-described is heated, while the vaporous mixture is cooled. whereby the watervapor in such mixture-is condensed, and the mix-' ture of ammonia vapor and water passes through the pipe" to the separator, where the water separatesfrom the vapor and flows through the pipe I! back into the generator- 54. The ammonia vapor flows from the separator through the pipe 18 to one end l1 0! 'a condenser I8, where such vapor is condensed,.the pressure upon the condensed vapor depending upon the temperature of.

the cooling water supplied to the end 80 of the condenser I8 by the pipeline 1G.. Theliquid ammonia flows from the condenser 11 through a pipe I! to anammonia receiver .55.. i I j The condensed water separated from the ain'- monia vapor in the separator 14 returns, as stated, to theend 54 or the generator 48 where it mixes. with the weak ammonia solution therein, and 1 this mixture flows thence through the pipe 88 and through the exchanger 66, where it gives up its heat to the solution flowing through the pipes 65 and 61. The cooled'condensate flows from the exchanger 66 throughthepipe 68 and into a cooler 10 where it is still vfurther cooled, and thence through the pipe ll back to the absorber G0 to absorb more ammonia; I I

Under certain conditions, for instance, when the water flowing through pipe I6 is at a temperature as high as approximately 70 F., it may be necessary to provide a water cooled condenser between the rectifier 64 and the separator 14,

' in order to condense all of the steam mixed with the carbon dioxide. Water which has been used elsewhere in the system may be used to cool this condenser. I

V From the receiver 55 liquid ammonia flows through the pipe 84 and past an expansion valve 56 to one end 51 of a condenser 58 where it refrigerates the compressed carbon dioxide discharged irom the compressor 52 and flowing through a pipe 8| to the opposite end 82 of said condenser 58. Such refrigeration of the carbon dioxide liquefles the carbon-dioxide, and liquid carbon dioxide is discharged through the pipe 43 Tests have shownthatgthe liquid ammonia evaporates in the condenser ,58 at a temperature of about minus8"1i.-- The compressor 52 is preferably;a' two stage' compressor, and carbon' dioxide leaves g -thatcompressor at a pressure oi about" 300,;pounds' per square inch absolute, It will fthusbei'seen that condensation .of thecarboni dioxide at this relatively low pressure isvery -easy,;-withf"the temperatures which can be .attained tlirough the use cit-ammonia as a refrigerant." I The ammonia vapor :returns from the condenser 5 8 through the pipe 159 to the absorber 60 where itis again absorbediin' the water therein, andthe cycle is repeated. If The heat of absorption developed in the absorber may be removed in' any desired manne as by cooling water.

Fig. 2 discloses an organization oi elements whichmay be added to the organization disclosed in Fig. 1, althoughFigr2 reproduces the illustration of the condenser 58. It the mechj anism disclosed in Fig. Ziisadded to that dis-.

inch absolute. Such "eva 'ai'iration reduces thetemperature of the 1iquid,and producesa certainamount of gaseous carbondioxide. The liq- 'uid, now at a temperature of approximately evaporator while the evolved gas flows through a' pipe 93 and a pipe 94 to the second stage Ii ot a two-stage compressor, where it is recompressed and led through apipe 96 to one. end I00 01 a condenser 58. Y The pipe 84 branchesas'at -84 and 84", the pipe 84' leading through an expansion valve 84' to the and 51-015 the-condenser, and a pipe 59' leading from said condenser'end II to the' pipe 59: and the branchtl' leads through an expansion valveiiff to the end 51 ofthe condenser 58', a pipe 59 leading from said condenser end 51" to thepipe 59. Thus, the compressed .carbon dioxide 'ied to the end I" of the. condenser 68' is refrigerated to eii'ect condensation thereof, and-the liquid is led .i'rom said minus 4.0 F., is allowed to. accumulate in the" condenser 58" through the pipe 81- back to the p p 83.

when a sufficient quantity of liquid carbon' dioxide at approximately minus 40 F. has accumulated in the evaporator 86, such liquid is permitted toflow through the pipe 81 and the expansion valve 88 into the press chamber 80.

the latent heat of such steam is wasted, and ex-' cept for the further fact that the cooling of the carbon dioxide which, according to the present invention, is efiected in the generator ,48 and the condensers 58 and 58' is, in ordinary practice, effected likewise by water coolers. Quite obviously, the utilization of the latent heat of the steam driven off from the boiler 30 to generate. refrigeration results in a very great saving of'energy; and just as obviously, the utiliza tion of the refrigeration so generated to cool the carbon dioxide in the liquefaction and solidification process will likewise result in a saving of energy because of the fact that much lower temperatures can be attained, with the result that liquefaction and solidification can be effected atmuch lower pressures.

It is not unusual for commercial plants to produce a thousand pounds of carbon dioxide per hour. In very efficient plants, and on the 0 basis of such production, approximately one pound of steam at approximately 230. F. will be boiled out of the boiler 30 for every pound of carbon dioxide produced. Thus it will be seen der such conditions, such a refrigerating systemwill produce a refrigerating effect equivalent to approximately thirty tons of' ice per day at a temperature of approximately zero degrees Fahrenheit. I

In less efflcient plants, from 2 to 8 pounds of steam will be produced in the lyeboilcr for every pound of carbon dioxide produced, and the temperature of such steam varies from about 230 to about 250 F. It will'be seen that, in such plants, still greater amounts of refrigeration can be produced'through the use of this steam, thereby effecting still greater economies;

When water at a temperature of from to 80 is used to remove the latent heat of the carbon dioxide in the liquefaction and solidification process, it is common practice to compress the carbon dioxide in a three-stage compressor to a pressure of 900 to 1000 pounds per square inch. Such a pressure is necessary in order to attain commer- If, instead of using water at '70? to F., am-

monia or some similar refrigerant at a temperature of zero degrees Fahrenheit is used to remove the latent heat of the carbon dioxide, liquefaction can be efiected at a pressure of approximately 300 pounds per square inch. A two-stage compressor can be used under these circumstances, whereby approximately one-third of the usual work ofcompression is saved.

, Under the conditions assumed, therefrigerating system will generate more refrigerating effect than is required to attain the indicated saving, and this excess refrigerating effect can be applied to the solidification of carbon dioxide. Under ordinary conditions, where water at 70 to 80 F. is used to cool the carbon dioxide, more than one-third of the total' work of compression required to solidify the carbon dioxide is done in the highstage cylinder. If ammonia, or some similar refrigerant at approximately zero degrees Fahrenheit is used instead of the cooling water, the high-stage of the recompression process can be eliminated.

The power necessary to provide the liquef ying compression is reduced by the presentprocess by an amount which is sufficient to eifect the recomproximately zero degrees Fahrenheit is used to cool the carbon dioxide.

It will thus be seen that the essential feature of the present invention lies in the utilization of the latenthcat of the steam,- necessarily produced in'the well known coke-lye process, and heretofore wasted, to generate refrigeration; and the utilization of that refrigeration to cool the produced carbon dioxide, whereby the power repression required to solidify the carbon dioxide, if ammonia or some similar refrigerant at ap-.

quired to liquefy or solidify the carbon dioxide is very materially reduced.

' It is not unusual, in commercial plants, to find that one kilowatt of purchased electric power is used in the production of eight to ten. pounds of solid carbon dioxide. I This power is, of course,

that which is required over and above the power supplied by the steam produced in the boiler I I. The use of the present process will certainly reduce the amount of purchased power to a negligible quantity, and will'probably eliminateit altogether.

I claim as my invention: I 1. In the coke-lye process of producingcarbon dioxide, the step of condensing in the generator. coil of an ammonia absorption refrigerating system, the steam driven off in the .lye boiler, sepa- 2. The method of producing non-gaseous car- I bon dioxide which comprises the steps of burn ingfuel to produce a gaseous mixture including carbon dioxide, utilizing the. heat of such com-' bustion to produce steam, using such steam to drive an engine, separating the carbon dioxide from such gaseous mixture by absorption in an aqueous solution, using the steam exhausted from the engine to drive off steam and carbon dioxide from said solution, condensing the steam, so driven off, in the generator coil of an absorption refrigerating system to generate refrigeration, separating the carbon dioxide from the condensate so formed, and utilizing the refrigeration so.

ous mixtureby absorption in Ian aqueous solution, heating such mixtureto drive of! steam andcarbon dioxide therefrom, condensing the steam,iso driven off, in the generator coil of an absorption refrigerating system to generate refrigeration, separating the carbon dioxide from the condensate so formed, and alternate- 1y compressing said carbon dioxide and cooling the. same by thegrefrigeration so generated; to effect a phase change thereof.

4. The method of utilizing waste energy developed in the coke-lye process of producing carbon dioxide, which comprises the steps of condensing the steam driven off from the lye boiler in they generator coil of an absorption refrigerating system, and utilizing the refrigeration so developed to cool the carbon. dioxide in the liquefaction process. I

5. Apparatus for producing non-gaseous carbon dioxide, comprising a chamber containing a liquid for absorbing carbon'dioxide, a second chamber, means connecting said chambers to permit liquid flow from one to the other, meansfor heating the liquid in said second chamber to drive off vapor and carbon dioxide therefrom, an absorptionrefrigerating apparatus including a generator heating coil, means for conducting the vapor and carbon dioxide from said second chamber to said heating coil, a compressor, means for conducting carbon dioxide from said coil to said compressor, a heat exchanger and means for bringing said carbon dioxide into heat-exchanging relation with refrigerant conducted from said refrigerating apparatus.

6. Apparatus for producing non-gaseous carbon dioxide, comprising a fuel burner, a boilerassociated therewith, a chamber containing a liquid for absorbing carbon dioxide, means for conducting the gaseous products of combustion at said burnerto said-chamber, a second'chamber, means connecting said chambers to'permit liquid flow from one to the other, a steam engine, means for conducting steam from said boiler to drive said engine, means for conducting steam exhausted from said engine into heat-exchanging relation with the liquid in said second chamber, whereby 1 vapor and carbon dioxide are driven olf there from, an absorption refrigerating apparatus includinga generator heating coil, means for con- .ducting the vapor and carbon dioxide from said second chamber to said heating coil, a compressor driven by said engine, means for conducting carbon dioxide from said coil to said compressor, a heat exchanger, and meansfor bringing said carbon dioxide into heat-exchangingrelation -with refrigerant conducted from said refrigerating apparatus.

7. The herein described process which com prises the steps of heating-{solution to drive therefrom a mixture of a gas and a vapor; condensing the vapor in the generator of an, absorption refrigerating system, and utilizing the re frigeration so generated to cool the gas.

8. The herein described process which comprises the steps of heating a solution to drive therefrom a mixture of a gas and a vapor, condensing the vapor inthe generator of an absorption refrigerating system, separating the condensate from the gas, and utilizing the refrigeration so generated to cool the gas.

9. The herein described process which comprises the steps of burning fuel to generate a gas, absorbing such gas in a liquid, utilizing the heat of combustion-of such fuel to drive off a mixture of such gas and a mass of vapor from s such liquid, condensing the vapor in the generator of an absorption refrigerating system, and utilizing the refrigeration so generated to cool the gas.

10. The herein described process which com prises the steps of burning fuel to generate a gas and to make steam-using the steam so generated to drive an engine, applying the heat of the steam exhausted from said engine to activate an absorption refrigerating system, and utilizing the refrigeration so generated to cool such gas.

11, Theherein described process which comprises the steps of burning fuel to generate a gas and to make steam, using the steam so generated to drive an engine, applying the heat ofthe steam exhausted from said engine to activate an absorption refrigerating system, compressing such gas by the operation of said engine, and utilizing the refrigeration so generated to cool such.-gas,"whcreby a change of phase of said gas a phase change.

13. The method of producing non-gaseous carbon'dioxide'which comprises the steps of burning fuel to produce a gaseous mixture including carbon dioxide, utilizing a portion of the heat energy generated upon the combustion of such fuel to drive an engine, separating the carbon dioxide from such gaseous mixture by absorption in a suitable liquid medium, utilizing a portion of such heat energy .to drive the carbon dioxide out of such liquid medium, utilizing a portion of such heat energy to generate refrigeration, utilizing the refrigeration so generated to cool the carbon dioxide, and compressing the carbon dioxide by the power developed by the engine to effect a phase change of said carbon dioxide.

14. The method of producing non-gaseous carbon dioxide which comprises the steps of burning fuel to produce a gaseous mixture including carbon dioxide, separating the carbon dioxide from such mixture, utilizing a portion of the heat energy generated upon the combustion of such fuel to drive an engine, utilizing a portion of s such heat energy to generate refrigeration, utilizing the refrigeration so generated to cool the separated carbon dioxide, and compressing the car-. bon dioxide by the power, developed by the engine to effect a phase change of said carbon dioxide.

.' a FRANKLIN B. HUNT. 

